What is "barrel of a boiler"

Barrel \Bar"rel\ (b[a^]r"r[e^]l), n.[OE. barel, F. baril, prob. fr. barre bar. Cf. Barricade.]

1. A round vessel or cask, of greater length than breadth, and bulging in the middle, made of staves bound with hoops, and having flat ends or heads; as, a cracker barrel. Sometimes applied to a similar cylindrical container made of metal, usually called a drum.

2. The quantity which constitutes a full barrel. This varies for different articles and also in different places for the same article, being regulated by custom or by law. A barrel of wine is 311/2 gallons; a barrel of flour is 196 pounds.

3. A solid drum, or a hollow cylinder or case; as, the barrel of a windlass; the barrel of a watch, within which the spring is coiled.

4. A metallic tube, as of a gun, from which a projectile is discharged.
   --Knight.

5. A jar. [Obs.]
   --1 Kings xvii. 12.

6. (Zo["o]l.) The hollow basal part of a feather.

   Barrel bulk (Com.), a measure equal to five cubic feet, used in estimating capacity, as of a vessel for freight.

   Barrel drain (Arch.), a drain in the form of a cylindrical tube.

   Barrel of a boiler, the cylindrical part of a boiler, containing the flues.

   Barrel of the ear (Anat.), the tympanum, or tympanic cavity.

   Barrel organ, an instrument for producing music by the action of a revolving cylinder.

   Barrel vault. See under Vault.

Boiler \Boil"er\, n.

1. One who boils.

2. A vessel in which any thing is boiled.

   Note: The word boiler is a generic term covering a great variety of kettles, saucepans, clothes boilers, evaporators, coppers, retorts, etc.

3. (Mech.) A strong metallic vessel, usually of wrought iron plates riveted together, or a composite structure variously formed, in which steam is generated for driving engines, or for heating, cooking, or other purposes.

   Note: The earliest steam boilers were usually spheres or sections of spheres, heated wholly from the outside. Watt used the wagon boiler (shaped like the top of a covered wagon) which is still used with low pressures. Most of the boilers in present use may be classified as plain cylinder boilers, flue boilers, sectional and tubular boilers.

   Barrel of a boiler, the cylindrical part containing the flues.

   Boiler plate, Boiler iron, plate or rolled iron of about a quarter to a half inch in thickness, used for making boilers and tanks, for covering ships, etc.

   Cylinder boiler, one which consists of a single iron cylinder.

   Flue boilers are usually single shells containing a small number of large flues, through which the heat either passes from the fire or returns to the chimney, and sometimes containing a fire box inclosed by water.

   Locomotive boiler, a boiler which contains an inclosed fire box and a large number of small flues leading to the chimney.

   Multiflue boiler. Same as Tubular boiler, below.

   Sectional boiler, a boiler composed of a number of sections, which are usually of small capacity and similar to, and connected with, each other. By multiplication of the sections a boiler of any desired capacity can be built up.

   Tubular boiler, a boiler containing tubes which form flues, and are surrounded by the water contained in the boiler. See Illust. of Steam boiler, under Steam.

   Tubulous boiler. See under Tubulous. See Tube, n., 6, and 1st Flue.